April 1: ORD

Today is April 1st. It's the 91st day of the year. 274 days remain. It's week 13 of the year.

Unless noted, the following data is based upon observations collected by the National Weather Service, Chicago, at O'Hare International Airport (ORD) between November 1978 and last year. ORD has been the official site of record for Chicago since Thursday, January 17, 1980.

According to the National Climatic Data Center (NCDC), the normal high is 53 and the normal low is 33. I've calculated the 32-year averages at 54 and 35.

On the warm side, last year, in 2010, the high was the new record high of 83 with the record-tying record warmest low of 54. The co-record warmest low of 54 occurred in 1963. In 2003 the high was 81 with a low of 39, a 42 degree spread. That high of 81 is just a degree short of the former record high of 82 which occurred in 1946. In 1999 the high was 62 with a low of 53. That low of 53 was just a degree short of the record warmest low. Other warm highs were 67 in both 1986 and 1994. Other warm lows were 46 in 2007 and 47 in 2000. 21 of the last 32 highs (66%) were in the: 40s (10) and 50s (11). On the warmer side, eight highs (25%) were in the: 60s (6) and 80s (2). There have been no highs in the 70s. On the cold side, three highs (9%) were in the 30s. Last year was incredible. The new record high of 83 occurred at 13:57 and the record-tying warm low of 54 occurred at 5:27. Rockford also established a new record high of 84 at 15:17. Some other highs: Midway (82), McHenry (83), Marengo (82), Barrington (81), Milwaukee (82 (rec)), Madison (81 (rec)), Green Bay (75 (rec)), Indianapolis (82 (rec)), St. Louis (87), Des Moines (86), Minneapolis (81), Paducah (80), Cincinnati (81), Louisville (84) and Lexington (80). This was just the 12th time in the past 140 years that a high reached 80 or higher (only 8.6%) on April 1, according to Tom Skilling at the WGN weather center.

In looking back through the years to the first April at O'Hare in 1959, the following instances were notable: In 1978 the high was a warm 67 with a low of 32, a 35 degree spread. In 1976 the high was 43 with a low of 37, a six degree spread. In 1974 the high was a warm 71 with a low of 41, a 30 degree spread and warm day. In 1972 the high was a cold 38 degrees. In 1970 the high was a cold 36 with a low of 34, a two degree spread. In 1969 the high was 64 with a low of 33, a 31 degree spread. In 1967 the low was a warm 47 degrees. In 1964 the low was a cold 19 degrees. In 1963 the high was 77 with a low of 54, a warm day and year of the co-record warmest low. In 1962 the high was a cold 40 degrees. In 1961 the high was a cold 37 with a low of 22, a cold day. In 1959 the high was 42 with a low of 38, a four degree spread.

More recently, we had a small spread of five degrees in 1979 (39/34). There were large spreads of 35 degrees in 1997 (62/27), 30 degrees in 1986 (67/37), 30 degrees in 1994 (67/37) and 31 degrees in 1984 (55/24).

On the cold side, in 1993 the high was 35 with a low of 27. A year earlier, in 1992, the high was 39 with a low of 28. Other cold highs were 39 in 1979, 41 in 1985 and 41 in 2002. The record low of 17 and record coldest high of 26 were set on the same cold day way back in 1881. 17 of the last 32 lows (53%) were in the 30s. Eight lows (25%) were in the cold 20s. Our most recent 20s low was 27 in 2002. Seven lows (22%) were in the warmer: 40s (5) and 50s (2).

Today is a major day in Chicago's snow history. 1970 was the first day of a two day storm. At O'Hare, 3.2 inches of a 7.2 inch total occurred. At Midway, 8.2 inches of a 10.7 inch total occurred. And in Rockford, 3.9 inches of a 6.7 inch total occurred.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:08 and sunrise is at 6:36. Sunset is at 19:19 and twilight ends at 19:47. There's a total of 12 hours, 43 minutes of daylight today and 13 hours, 39 minutes between twilights. We gained three minutes of daylight from yesterday. Tomorrow twilight begins at 6:06 and sunrise is at 6:35. The moon is waning crescent and will be new in two days at 9:32. Illumination was 5% at midnight, will be 3% at noon and 2% at midnight tonight. Moonrise is at 5:24 this morning. Moonset is at 17:50 this afternoon. Moonrise is at 5:47 tomorrow morning. Moonlight time is 12 hours, 26 minutes which is 37 minutes longer than yesterday.

April Fool's Day is today. The warm part of Spring (Warm Spring) begins in 12 days on April 13. Warm Spring runs for 52 days, through June 3. High temperatures in this period are usually in the 50s, 60s and 70s. Warmer 80s and 90s occur infrequently. -Bernie-